Before we get into the fascinating story of the Soviet (specifically the Angstrem) Z80 clone it’s good to understand a bit about the IC industry in the USSR.  There were many state run institutions within the USSR that were tasked with making IC’s.  These included analogs of various western parts, some with additional enhancements, as well as domestically designed parts.  In some ways these institutions competed, it was a matter of pride, and funding to come out with new and better designs, all within the confines of the Soviet system.  There were also the various Warsaw Pact countries (Bulgaria, Czechoslovakia, East Germany, Hungary, Poland and Romania), that were aligned with the USSR but not part of it.  These countries had their own IC production, outside of the auspices and direction of the USSR.  They mainly supplied their own local markets (or within other Warsaw Pact countries) but also on occasion provided ICs to the USSR proper, though one would assume an assortment of bureaucratic paperwork was needed for such transfers.

This resulted in some countries developing similar devices, at rather different times, or different countries focusing on different designs.  East Germany was all in on the Z80, Romania, Poland and Czechoslovakia made clones of the 8080, Bulgaria, the 6800 and 6502. They were though, seperate from the USSR’s own institutional system, so while East Germany had a working Z80 in the early 1980’s the USSR did not.  It is this distinction we will focus on today

This article is largely from guest author Vladimir Yakovlev, translated from Russian, and edited/expanded by me.

By the end of the 80s – beginning of the 90s, clones of the British Sinclair ZX Spectrum computer, a simple, cheap computer with a huge library of games originally released in 1982, were being distributed in the USSR. The “strapping” of the central processor instead of the original ULA microcircuit was done on small logic microcircuits of the 555 (74LS) series and the like, but the Z80 itself had to be bought from abroad. Naturally, the thought arose, to start making the processor yourself. After all, the processor itself, developed in 1976 for the microelectronic industry, was not too complicated.

In 1990, the development of an analogue of the Z80 was organized in Zelenograd near Moscow at the Scientific Research Institute of Precise Technology (NIITT) and the “Angstrem” plant. Initially, Zelenograd was conceived as a center of the textile industry, but was later reoriented to the development of electronics and microelectronics by Nikita Kruschev after he visited Silicon Valley (California, USA) in 1959. To this day, Zelenograd has retained the status of a scientific center and the informal name “Russian Silicon Valley”.

The chief designer was appointed Yuri Otrokhov, who had previously led similar developments. Otrokhov, who served as a tanker in his youth (military service being mandatory in the USSR), called the project the T34 microprocessor.

Otrokhov: “T-34VM1 is the internal designation of the KR1858VM1 processor, assigned by me at the stage of development and production in honor of my first tank, on which I learned to drive.”

Here is one of the versions of the creation of the clone, outlined by one of the employees of NIITT at that time, Boris Malashevich [1]:

“Otrokhov, like his colleagues in the department, knew how to develop original microprocessors, but they had not yet had to reproduce analogs. Therefore, the developers included specialists from NIITT divisions who are able to restore the electrical circuit of the IC according to its topology. For 9 months after four iterations, they managed to make an NMOS microprocessor T34VM1 (KM1858VM1, KR1858VM1) – a complete analogue of the Z80A microprocessor, to be made using a 2-micron technology” (The original Zilog version was on a 4 micron process).

While Otrokhov and his team worked at Angstrem to make a NMOS Z80, a similar team was working at ‘Transistor’ in Minsk Belarus to make a CMOS version, later known as the KR1858VM3.

Due to the incredible popularity and demand for the Z80, many analogue manufacturers worked without a license, so in total less than half of all Z-80 produced were licensed products from Zilog or its official partners (SGS, Mostek, etc).

From an interview with the creators of the Z80 [2]:

Faggin: Yes, we were concerned about others copying the Z80. So I was trying to figure what we could
do that that would be effective, and that’s when I came across an idea that if we use the depletion load
the mask that doesn’t leave any trace, then I could create depletion load devices that look like
enhancement mode devices. And by doing that we could trick the customer into believing that a certain
logic was implemented, when it was not. Then I told Shima, “Shima, this is the idea how to implement
traps. Put traps, you know, figure out how to do the worst possible traps that you can imagine,” and then
Shima with his mind, that was steel mind, was able to actually figure out a bunch of traps that he could
talk about.
Shima: I didn’t count [on] talking about that mostly. I placed six traps for stopping the copy of the layout
by the copy maker. And one transistor was added to existing enhancement transistors. And I added a
transistor looks like an enhancement transistor. But if transistors are set to be always on state by the ion
implantations, it has a drastic effect on very much. I heard from NEC later the copy maker delayed the
announcement of Z80 compatible product for about six months. That is what I got from NEC. And finally
a total transistor of Z80 became 8,200 while a total of transistor of 8080 was 4,800.

In the course of the design, due to the fact that the development team had specialists in both the creation of new ICs and the reproduction of analogs, Zilog’s tricks aimed at copy protection were identified and decrypted. For example, the topologist saw the 3-Input-NAND Gate element, but this element worked as 2-Input-NAND Gate. The topology and layout of the resulting clone was different, but the functionality did not differ from the original. At first, it was possible to identify such traps, making sure that the circuit was inoperable, only by examining the circuit elements inside the die using probe analyzers. But, having understood the principle of constructing traps, a mechanism for their detection was also developed. As a result, it was possible to make a full-fledged analog of the Z80, although the electrical circuit and topology of the T34MV1 had some differences.

The German Connection

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NEC uPD78C11 ES for Mask ROM

Most microcontrollers store the program they run in ROM, most of the time this ROM takes the form of a Mask ROM.  This means that its set at the factory when the die is being made, one layer (or more) of the die contains the ROM and the program is hardcoded into the device.  Development versions almost always exist that allow programs to be developed before the mass produced Mask ROM chip, but still the mask must be tested.

This is such an example from NEC.  It is a engineering sample of a uPD78C11 made in 1988.  the 78C11 (and many others in the 78k family) used a 64 pin QUIP (Quad Inline Package),  The 2 rows of staggered pins allowed for a 64 pin DIP in a much smaller foot print.  The only problem was these chips are extremely delicate.  They were designed to be soldered in and never removed.  The standard package was plastic, but for the sake of testing, these are ceramic (its a bid easier to place/bond the dies on small batches on a ceramic package)

The NEC 78k family was and continues to be very popular.  Its current version (the RL78) is made by Renesas, which was formed when Mitsubishi, Hitachi, and NEC joined their semiconductor businesses.  78K processors powered everything from word processors to washing machines and sewing machines.  Now they are also commonly found in automotive applications.

NEC uPD7811G – 1988

Like many modern microcontroller families the NEC 78k traces its lineage back to the 1970’s.  The family first appeared in 1980 as the uPD7801.  The 7801 was a microcomputer based on the NEC 780 which was NEC’s version of the Zilog Z80.  The 781x series released in 1982 expanded on the architecture by including an ADC, as well as a full 16-bit ALU (versus the 8-bit from the 780 and 780x) that even supported 16-bit multiply and divide.  The 16-bit ALU made it a simple task for NEC to again extend the architecture to a 16-bit version.  The instruction set was similar, though the naming was different then the Z80.  In 1985 NEC moved the 78k line to a CMOS process, reducing power requirements and increasing the max clock from 12 to 15MHz.

The inclusion of many peripherals made the 78k a popular choice for many embedded applications.  Its continued availability, and wide code base have allowed it to continue to thrive.  And once again, a ‘modern’ MCU is based on a design from the 1970’s.  Processor architectures rarely die, they just continue morphing.

Zilog Packages available in 1985

Last week we showed you an educational kit from Zilog showing the process involved in making and assembling a Z80 processor, from polished wafer to packaging.  Zilog also made a kit for marketing the various packages used.  This kit contains a shrink DIP 64 pin socket, a shrink DIP 64pin package, a 48 pin DIP and 40 pin DIP, all the common packages used at the time.

Zilog Packages – Z8 Z80 Z800 and Z8000

At the time is a little hard to track down as no date is provided with this kit.  We can get very close though looking at the back where Zilog lists which devices are available in these packages.  The usual Z80 and Z8000 series are both there as well as the Z8 microcontroller family.  The one odd-ball is the Zilog Z800.  The Z800 was an upgraded Z80 released in 1985, adding on chip cache an MMU and a vastly expanded instruction set (over 2000 instruction/addressing modes).  It was wholly unsuccessful partly do to bad marketing by Zilog, and partly because it did more then it needed to. It never entered mass production, and by 1986 Zilog has redesigned it, converted the design to CMOS (from NMOS) and released it as the Z280 which met the same fate as the Z800.  It seemed that making an overly complicated Z80 wasn’t what the market wanted.  THe Z180 (designed by Hitachi) and the Zilog eZ80 (released in 2001), have enjoyed much wider success, mainly because they kept closer to the simplicity of the original Z80.

So when was this kit put together? Likely 1985, as the Z800 was nly talked about for a few months before quietly being put away.

Technologizer has published a very interesting article on Osborne Computers, and its founder, Adam Osborne.  Osborne computers was started 30 years ago (April 3rd 1981).  They were the fastest growing, and fastest failing company in Silicon Valley, impressive even today. Adam Osborne was one of the most important people in Silicon Valley (along with Bill Gates and Steve Jobs).  His books in the 70’s are still invaluable resources for collectors, I have several editions of ‘An Introduction to Microcomputers’ which provide an invaluable reference to some of the chip designs of the 1970’s and early 1980’s.

The Osborne 1, the first wildly successful portable, was based on a Zilog Z80A processor and ran the then popular CP/M OS.  If it wasn’t for cash flow problems, Osborne computers may very well have still been making computers today.  It is also interesting that Mr. Osborne had a habit of picking designs that ended up to be not very successful (he chose the Zilog Z8000 and Intel 8089 I/O processor as ‘Chips of the Year’ in 1980)

In 1974 Federico Faggin left Intel after working on the 8-bit 8080 processor.  He formed a company called ZiLOG and developed a much improved version of the 8080 called the Z80.  It was released in 1976 after only 18 months of design.  The Z80 was faster, cheaper, and simpler to build around then the 8080 and enjoyed extremely wide use.  ZiLOG designed the CPU but it was marketed differently than most at the time.  Any company could purchase a license to the design, and build them royalty free.  They were also free to do with the design as they pleased.  This resulted in dozens of companies making clones/versions of it. The Soviets made unlicensed copies as well. In fact other companies made more Z80s then ZiLOG did themselves.

Zilog Z-80 CPU 8400X CS – 1979 2.5MHz

The Z80 was not the only processor that ZiLOG made.  Some of the processors/part numbering can be a bit confusing so we’ll look at each family and part that Zilog made up through 1985.  After 1985 CMOS designs came out as well as dozens of variations.  We just want to look at the first ten years of ZiLOG.

Zilog Z8300-3PS – 1984 2.5MHz

The Z80 itself was, of course, similar to the 8080 but single voltage, and only required a single clock phase.  It was available in speeds of 2.5-8MHz.  ZiLOG also made a low-power version known as the Z80L (Z8300) that ran from 1-2.5MHz.  That’s really all there was to the Z80 family up through 1985.

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In a recent deal to try to solve their cash problems, and streamline profitability, Zilog sold off its secure transaction products (namely 32bit ARM processors) to Maxim (who through the purchase of Dallas, makes many MCS-51 controllers),  They also sold off their wireless division to Maxim (and the software portion of this to a company called UEI)

What does this leave? Essentially the classic Z80 processor that has been around for the last 33 years, and all the related extentions there of.  Old designs tend to stick around for a long time, and the Z80 is no exception.

Source: EE Times